The best replacement for moonstone is ms marvel.

The best alternatives to moonstone are rated as following:
★★★★★  ms marvel
★★★★★  pearl
★★★★★  labradorite
★★★★  opal
★★★  opalite
★★★  alexandrite
★★  mother of pearl
★★  horseshoe
★  rainbow moonstone
★  grey moonstone
★  agate
  songbird

Your alternative for moonstone is not listed? Suggest!
Speaking about moonstone, one probably shouldn't forget about sunstone.

Other search terms related to moonstone and their ratings are:
★★★★★ sunstone
★★★★ eevee
You have in mind a companion for moonstone and it is not yet here? Propose!



Google Trends

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moonstone
ms marvel
pearl